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[dinosaur] Middle Triassic Xingyi Fauna marine reptiles + bothremydid from Portugal + End-Triassic mass extinction volcanism





Ben Creisler
bcreisler@gmail.com


Some recent non-dino papers:


Hao Lu, Da-Yong Jiang, Ryosuke Motani, Pei-Gang Ni, Zuo-Yu Sun, Andrea Tintori, Shi-Zhen Xiao, Min Zhou, Cheng Ji & Wan-Lu Fu (2017)
Middle Triassic Xingyi Fauna: showing turnover of marine reptiles from coastal to oceanic environments.
Palaeoworld (advance online publication)
https://doi.org/10.1016/j.palwor.2017.05.005
http://www.sciencedirect.com/science/article/pii/S1871174X17300318


The late Ladinian (Middle Triassic) Xingyi Fauna from the Zhuganpo Member of the Falang Formation yields abundant and well-preserved marine reptiles. Bed-by-bed excavation at Wusha in Xingyi of Guizhou Province reveals two marine vertebrate assemblages in a fossiliferous horizons that span 5.1 m in total thickness. The lower assemblage is marked by the near-shore sauropterygians, including the pachypleurosaur Keichousaurus, the nothosaurians Nothosaurus and Lariosaurus, with a strong paleobiogeographic affinity to western Tethys. The upper assemblage consists of oceanic ichthyosaurs and pistosaurs, including the large shastasaurid ichthyosaur Guizhouichthyosaurus, the euichthyosaur Qianichthyosaurus, pistosaurs Yunguisaurus and Wangosaurus, and the thalattosaur Xinpusaurus, with a closer paleobiogeographic affinity to North America. The coastal pachypleurosaur and nothosaurid sauropterygians disappeared in the upper assemblage, suggesting that they were replaced by an oceanic marine reptile community that emerged. The reptilian composition of the upper assemblage is similar to that of the Guanling Biota, which is of the Early Carnian (Late Triassic) in age and thus somewhat younger than the Xingyi Fauna. The ecological turnover of marine reptiles from near-shore to the open ocean community corresponds to the paleoenvironmental changes indicated by lithofacies analysis, δ13C and the global sea level changes.


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A. Pérez-García, M.T. Antunes, F. Barroso-Barcenilla, P.M. Callapez, M. Segura, A.F. Soares & A. Torices (2017)

A bothremydid from the middle Cenomanian of Portugal identified as one of the oldest pleurodiran turtles in Laurasia.

Cretaceous Research (advance online publication)

doi: https://doi.org/10.1016/j.cretres.2017.05.031

http://www.sciencedirect.com/science/article/pii/S019566711730099X


 

Highlights


A turtle shell from the middle Cenomanian of Nazaré (Portugal) is studied here.

It corresponds to the second member of Bothremydidae identified in Portugal.

It is one of the scarce bothremydid remains known in pre-Santonian Laurasian levels.

It corresponds to Algorachelus, the oldest Bothremydidae in the Laurasian record.

The oldest known dispersal event of Pleurodira to Laurasia is better understood.


Abstract


The relatively complete and well preserved shell of a turtle, from the middle Cenomanian of Nazaré (Portugal), is studied here. It is recognized as a member of the crown group Pleurodira and, more specifically, the Bothremydidae. Pleurodira are one of the two lineages of modern turtles, their origin being in Gondwana. Pleurodira are very abundant in the uppermost Cretaceous record of Europe. However, this new finding is one of the few occurrences in the lower Upper Cretaceous of Laurasia. A single member of Bothremydidae had so far been identified in Portugal: the late Campanian-early Maastrichtian Rosasia soutoi. It is the only Cretaceous turtle that is endemic to that country both at specific and at generic levels, being exclusive of Portugal. The taxon from Nazaré is identified as Algorachelus peregrinus, this form is also present in the contemporaneous beds in Spain, and is the oldest member of Bothremydidae in Laurasia. Algorachelus peregrinus is confirmed here to be a coastal form, which facilitated its spread. The two oldest known bothremydids from Laurasia, the European A. peregrinus and the North American Paiutemys tibert, are compared for the first time. They are recognized as closely related taxa. This study provides new data allowing a more precisely characterization of the oldest so far known dispersal event of Pleurodira in Laurasia, which was performed by an African lineage of Bothremydidae that reached the east coast of the Atlantic Ocean at least in the middle Cenomanian, and the west region of that Ocean at least in the late Cenomanian.


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J.H.F.L. Davies, A. Marzoli, H. Bertrand, N. Youbi, M. Ernesto & U. Schaltegger (2017)

End-Triassic mass extinction started by intrusive CAMP activity.

Nature Communications 8, Article number: 15596 (2017)

doi:10.1038/ncomms15596

https://www.nature.com/articles/ncomms15596




The end-Triassic extinction is one of the Phanerozoic’s largest mass extinctions. This extinction is typically attributed to climate change associated with degassing of basalt flows from the central Atlantic magmatic province (CAMP). However, recent work suggests that the earliest known CAMP basalts occur above the extinction horizon and that climatic and biotic changes began before the earliest known CAMP eruptions. Here we present new high-precision U-Pb ages from CAMP mafic intrusive units, showing that magmatic activity was occurring 100 Kyr ago before the earliest known eruptions. We correlate the early magmatic activity with the onset of changes to the climatic and biotic records. We also report ages from sills in an organic rich sedimentary basin in Brazil that intrude synchronously with the extinction suggesting that degassing of these organics contributed to the climate change which drove the extinction. Our results indicate that the intrusive record from large igneous provinces may be more important for linking to mass extinctions than the eruptive record.



News:

https://phys.org/news/2017-06-volcanoes-referees-life-earth.html